Machine for inspecting glass containers

ABSTRACT

A machine for distinguishing blisters from checks on the finish of a glass container. The captured objects are located in a band to define a cluster. The cluster is evaluated to determine whether it is a multiple cluster and each defined cluster is evaluated to distinguish a check from a blister.

The present invention relates to machines, which inspect glasscontainers for defects, and more particularly, to a system whichinspects for checks (cracks) in translucent glass containers.

BACKGROUND OF THE INVENTION

In the glass container industry, small cracks, or fracture in the glassare referred to as “check defects”. Checks can range from submillimeters to several hundred millimeters and can be oriented at anydirection from vertical to horizontal. Glass is not a crystal-linestructure by nature, but most cracks propagate roughly along a plane ofsome orientation in space mostly determined by the shape of the glass atthat location. Most of these crack defects will drastically weaken thebottle, often causing it to rupture or to leak. Therefore, it is verylikely that a bottle manufacturer will remove a container with a checkbefore it reaches filling plants. Checks appearing near the mouth of thecontainers are called finish checks. In the glass bottle industry, theterm “container finish” refers to the portion of the bottle that definesthe mouth, threads or beads, and the ring. The upper surface of themouth is referred to as the sealing surface.

Another anomaly, which can also be present are bubbles. A bubble resultswhen gas is trapped in the glass. When the bubbles are large they arereferred to as a blister and when the bubbles are small, they arereferred to as a seed. The presence of bubbles, while affecting theappearance of the bottle, do not necessarily require the rejection ofthe bottle and an operator may allow such a bottle to be packed. Forpurposes of this application, the word blister will include a seed.

The following U.S. Pat. Nos. 4,701,612, 4,945,228, 4,958,223, 5,020,908,5,200,801, 5,895,911, 6,104,482, 6,211,952, and 6,275,287 all relate todevices that detect defects in the finish of a container.

OBJECT OF THE INVENTION

It is an object of the present invention to provide an apparatus forinspecting glass containers, which can differentiate vertical,horizontal, and any other angle cracks (checks) from blisters.

Other objects and advantages of the present portion of this inventionwill become apparent from the following accompanying drawings, whichillustrate, in accordance with the mandate of the patent statutes, apresently preferred embodiment incorporating the principles of theinvention

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will become apparent from the following accompanyingdrawings which illustrate, in accordance with the mandate of the patentstatutes, a presently preferred embodiment.

FIG. 1 is an oblique elevational schematic view of a prior artinspection station of a machine for inspecting glass containers forchecks and other defects;

FIG. 2 is a schematic top view of the container at the prior artinspection station showing the light axes of a pair of light sources andthe camera;

FIG. 3 is a schematic elevational view showing the light axes of theprior art light sources and camera shown in FIG. 2;

FIG. 4 is a control drawing showing how an unwrapped image is defined;

FIG. 5 is a view, taken from the camera, of the finish area of thebottle shown in FIG. 1, illustrating images captured each θ (theta)degrees of rotation of the bottle about its vertical axis through anangle φ (phi);

FIG. 6 is a schematic illustration of the unwrapping process illustratedin FIG. 4;

FIG. 7 is a presentation of 10 images of an object captured through 11locations spaced θ (theta) degrees apart through an angle of φ (phi)degrees with the center of the object plotted;

FIG. 8 is presentation similar to that of FIG. 7 showing only theobjects in band 1-2;

FIG. 9 is presentation similar to that of FIG. 7 showing only theobjects in band 2-3;

FIG. 10 is presentation similar to that of FIG. 7 showing only theobjects in band 3-4;

FIG. 11 is a control drawing showing the structure of the control fordetermining whether a captured object is a check or a blister; and

FIG. 12 is a control drawing illustrating the structure for identifyinga bottle for rejection.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In a machine for inspecting glass containers (bottles), the containers10 are transported vertically along a conveyor 12 to an inspectionstation illustrated in FIG. 1. The conveyor may be a linear belt or aturret type feed system. A container 10 is engaged by upper and lowerrear pairs of idler rollers 14 and a front drive wheel 16 so thatrotation of the drive wheel in the clockwise direction will rotate thecontainer in the counterclockwise direction. There is conveyor dwell ofsufficient duration at the inspection station so that the container canbe rotated more than 360 degrees while inspection takes place. Acontainer present sensor 18 will sense the presence of a container atthe inspection station. Conical light sources (Light Source #1/20 andLight Source #2/21) which can be configured from L.E.D.'s, illuminatethe finish portion of the container and a Camera/22 images the finishportion. As can be seen from FIGS. 2 and 3, the Light Axis for eachlight source, which is in the positive “Z” plane of the container, ishorizontal, and intersects the axis “A” of the container. The two lightaxes are orthogonal to each other (the light axes are horizontal and 90degrees related), and 45 degrees to a vertical plane including theCamera Detector Axis. The Detector Axis for the Camera/22, which islocated in the negative “Z” plane, is approximately 45 degrees fromhorizontal (the camera bisects the horizontal light axes). With thisrelationship, the camera is looking at a dark field and is ideallyseeing only light coming from checks and blisters. The light sources andcamera are supported by structure 28 that can be vertically displacedand horizontally displaced to reposition the system for differentheight/diameter containers.

To start an inspection, the machine will transfer a container to theinspection station and following a time sufficient for the rotation ofthe container 10 to become stable, the Control 50 (FIGS. 4, 11 and 12)will begin the inspection. The Control will Rotate The Container AboutAxis Through Desired Angle 42 (FIG. 4). FIG. 5 illustrates theappearance of an anomaly 30 (a check or a blister) on the finish of thecontainer, as it would appear if captured by the camera as the bottlerotated through θ (theta) degree increments. As illustrated, thecontainer has an anomaly which is captured at ten of the elevenlocations spaced θ (theta) degrees. Such could occur by operating thecamera every time the bottle rotates θ (theta) degrees or could occur byholding the camera open for a prolonged period while strobing the lightsource each θ (theta) degrees. The anomalies are shown located within anangle of interest φ (phi) defining a partial elliptical path. TheControl 50 proceeds to Capture A Selected Number Of Images At θ (theta)Degree Increments 44 and the Control will then Locate The Upper EdgePoints Of Container 60. This edge 61 is shown in FIG. 5. The Controlwill then Fit Curve 62 to these edge points. This could be done usinglinear regression techniques. The fit curve 63 is shown in FIG. 6. TheControl then proceeds to Determine Vertical Peak Of Fitted Curve 64.This peak 65 is also shown in FIG. 6. The Control than proceeds toDefine Horizontal Line Through Peak 66 (line 67 in FIG. 6) and proceedsto Unwrap Image 68. This procedure is shown in FIG. 6 with verticaloffsets 69 which are defined by the number of pixels required to shiftthe fitted curve 63, at each vertical row, vertically to the peaktangent line 67. The Control will then Define The Center Of An AnomalyIn Each Captured Image 46.

FIG. 7 is a schematic presentation of the linear array of the ten imagesof an object captured through the 11 locations spaced θ (theta) degreesapart through the angle φ (phi) degrees with the center of the objectsplotted showing their “Y” location as a function of three horizontalbands and with their “X” location corresponding to its angularincrement. While the preferred embodiment unwraps the elliptical imageto define horizontal bands, the bands could be elliptically matched tothe pattern of the captured objects. FIGS. 8-10 are schematicpresentations of the objects sorted into each of the bands (1-2, 2-3,and 3-4) presented in FIG. 7. Each band represents a horizontal scanline or lines (a band could, for example be five horizontal scan lines).The width of each band (“B”) is shown as settable. Referring to FIG. 11,the Control 50 will Determine Objects In “N” Horizontal Bands “B” High70. The objects within a band define a “cluster”. The cluster objectsidentified in FIGS. 8 through 10 are:

Band 1 (1-2)—objects B, C, G, H, I;

Band 2 (2-3)—objects A, B, C, E, F, G, H, I, J, K;

Band 3 (3-4)—objects A, E, F, J, K;

The Control then proceeds to Define Band Having Most Objects As FirstCluster 72. In the above illustration, Band 2 has the most objects (10).If two bands have an identical number, the Control could pick either onefirst. The Control then proceeds to Remove Common Objects From OtherBands 74. The bands thus become:

Band 2 (2-3)—objects A, B, C, F, F, G, H, I, J, K;

When the Control asks the query Does Band With Next Highest Count OfObjects Have Objects Common To Other Bands? 76, the answer will be inthe negative—Band 2 has all the unique objects. No further revisions ofthe bands will take place. The objects in Band 2 will then be identifiedas a cluster.

Alternately, the bandwidth “B” could be set at 10 scan lines and all ofthe ten objects could be located within the single band and treated as asingle cluster.

The Control next asks Does Any Cluster Have Gap(s) at least “X” ObjectsWide (X is settable) 78. In the event the query is answered in theaffirmative, the Control will Define Additional Clusters 79. If “X” wasset at three, this query for Band 2, would be answered in the negativesince there is a single gap one object wide. Had this gap been threeobjects wide (D, E, & F missing, for example) the Control would definethe objects to the left of the gap (A, B, & C) as one cluster and theobjects to the right of the gap (G-K) as a second cluster. It has beenfound that blisters generally have very small gaps and that a large gapindicates one or more checks. If the operator does not want to use thistool, “X” can be set at 12, for example.

The Control will then Define Maximum Separation Of Objects In EachCluster 80. Cluster 1 has ten spacings separating A from K. The Controlnow determines whether the cluster is a check or a blister. This is doneby answering the query “Max Separation of “N” Cluster≧(greater than orequal to) “Z”?” 82. Assuming Z is 8 (a settable input), when thisinquiry is answered for Cluster 1 the answer will be yes and the Controlwill Define “N” Cluster As Blister 86. Had the separation been less than8, the Control would Define “N” Cluster As Check 84. This procedure willbe repeated for each cluster.

If desired, a decision could be made at this point to pass all blistersand reject all checks but additional choices are provided by theControl. FIG. 12 illustrates the structure of the Control 50 fordiscriminating between a Blister or Check that will not result in abottle being rejected and one that will. The Control answers the query“Have All Clusters Been Defined As A Blister Or A Check! 90”. If theanswer is “yes”, the Control answers the query “Is Area Of Single ObjectIn A Blister Cluster≧(greater than or equal to) AA!” Or Is Total Area OfAll Objects In A Blister Cluster≧(greater than or equal to) BB! Or IsNumber Of Objects In A Blister Cluster≧(greater than or equal to) CC! orIs Total Area Of All Objects In All Blister Clusters≧(greater than orequal to) DD! Or Is Total Number Of Objects In All BlisterClusters≧(greater than or equal to) EE! 92. If this query is answered inthe affirmative, the Control will issue a Bottle Reject Signal 94.

The Control will also answer the query “Is Area Of Single Object InCheck Cluster≧(greater than or equal to) FF?” Or Is Total Area Of AllObjects In A Check Cluster≧(greater than or equal to) GG? Or Is NumberOf Objects In A Check Cluster≧(greater than or equal to) HH? or Is TotalArea Of All Objects In All Check Clusters≧(greater than or equal to) II?Or Is Total Number Of Objects In All Check Clusters≧(greater than orequal to) JJ? 96. If this query is answered in the affirmative, theControl will also issue a Bottle Reject Signal 94.

1. A machine for inspecting the finish area of a glass containerrotating at an inspection station and discriminating between a blisterand a check comprising: a rotating device for rotating a bottle aboutits axis; a lighting device for illuminating the finish area of therotating bottle; a camera for imaging the finish area of the rotatingbottle; and a control configured to; define a cluster of objectscaptured by said camera at a predetermined number of angular incrementsof rotation; determine whether there is at least one gap having aminimum size between objects in the cluster; define additional clustersas a function of the number of such gaps; define a selected separationof objects; and define a cluster as a check where the farthest separatedobjects in a cluster are separated less than the selected separation. 2.A machine for inspecting the finish area of a glass container rotatingat an inspection station and discriminating between a blister and acheck according to claim 1, wherein said control further comprises meansfor defining a cluster as a blister where the farthest separated objectsare separated more than the selected separation.
 3. A machine forinspecting the finish area of a glass container rotating at aninspection station and discriminating between a blister and a checkaccording to claim 1, wherein said control configured to define acluster of objects captured by said camera at successive time incrementscomprises means for defining a band including the cluster.